school buses spew pollution into young lungs

and i'm sure a lot of passenger buses are no better.

science news, may21, 2005

ENVIRONMENT
School buses spew pollution into young lungs

Reducing school bus emissions could be a cost-effective way to cut children's exposure to diesel fumes. Researchers reached that conclusion after finding that school bus passengers may inhale heavy doses of the vehicle's pollution.

To understand school buses' effects on air quality, Eduardo Behrentz of the University of California, LosAngeles and several colleagues drove six buses of various ages on a total of 16 runs along actual routes in and around Los Angeles. On about half the runs, the bus windows were open.

During the runs, the scientists continuously fed a nonreactive tracer gas, sulfur hexafluoride, to the buses' exhaust systems. Devices at the front and rear of each bus measured the tracer. Thes cientists then estimated the amount of exhaust particles that passengers would inhale.

On average, the rear of each bus' interior is one-third more polluted than the front, Julian D. Marshall of the University of California, Berkeley and Behrentz report in the April 15 Environmental Science & Technology. Moreover, they found, older buses and buses driven with the windows closed carrymore onboard air pollution than other buses do. For example, a 30-year-old bus in the study generated twice as much onboard pollution as a 10-year-old bus did. Closing the windowsslightly increased passengers' pollution exposure on a 3-year old bus but tripled it on the 30-year-old one. --- B. H.